In St. Tropez, France, on Sunday, sources tell Us Weekly that the famous exes, who split in 2009 after Brown was charged with assaulting then-girlfriend Rihanna, found a way to arrange an undercover meeting.

The "Where Have You Been?" songstress, 24, has been sunning herself throughout the South of France this past week, but made an addendum to her schedule when she got word of Brown's arrival.

"Rihanna knew Chris was on his way [to St. Tropez] and actually changed her plans late Friday night late after calling Chris from the yacht's satellite phone," a source tells Us.

Brown, 23, who chartered an impressive yacht complete with a submarine, two helicopter landing pads and a swimming pool, was seen mooring the boat next to Rihanna's off of the town's Pampelonne Beach. The "Turn Up the Music" singer is said to have rented the impressive yacht with Swizz Beatz and Ludacris -- for a whopping $400,000 a week -- for an upcoming music video.

"Rihanna went and partied hard with the guys on their yacht," the source says.

Another source adds that Brown's current girlfriend, Karrueche Tran, was also aboard. "I don't know if Rihanna even knew that she was there!"

Although Rihanna and Brown avoid stepping out in public together, the singer has gone on the record to defend her contact with her ex, namely, their musical collaboration on a remix of her song "Birthday Cake."

"It never occurred to me how this was going to be a problem," she explained to Esquire UK in June. "I thought people were gonna be surprised that we finally did a record together, but I didn't see how people could think it was a bad thing, you know? In my mind, it was just music. ... I could never see anything wrong with making music."